Field of the Invention
The present invention relates generally to a pasha processing apparatus for fabricating electronic substrates in which plasma is excited by RF power applied between electrodes. More specifically, the present invention relates to a liner assembly disposed inside the plasma processing apparatus for balancing RF current flow launched from the electrodes.
Description of the Prior Art
Electronic devices, such as flat panel displays and integrated circuits, commonly are fabricated by a series of process steps in which layers are deposited on a substrate and the deposited material is etched into desired patterns. The process steps commonly include physical vapor deposition (PVD), chemical vapor deposition (CVD) plasma enhanced CVD (PECVD) and plasma process. Specifically, the plasma process requires supplying process gas mixture to a vacuum chamber called a chamber body, and then applying electrical or electromagnetic power (RF power) to excite the process gas to a plasma state. In other words, the process gas is excited into the plasma by the RE current launched from electrodes. The plasma decomposes the gas mixture into on species that perform the desired deposition or etch process.
Generally, the substrate can be delivered from the transfer chamber to the chamber body via transfer mechanisms (e.g. robot blade) and be placed on a support assembly (e.g., susceptor or pedestal) of each chamber body for processing. Furthermore, the chamber body may also comprise a chamber liner to protect the inner walls of the chamber body. Please refer to FIG. 1A. FIG. 1 illustrates a perspective view of the traditional chamber liner. As shown in FIG. 1A, to receive the substrate delivered from the transfer chamber, the chamber liner 90, disposed inside a chamber body, usually has a corresponding slot 902 for receiving the substrate which is aligned with the slit valve tunnel of the chamber body.
During substrate processing, RF currently launched from the electrodes returns to the power source on the surface of the chamber liner. Since the RF return current does not travel across the gap defined by the slot 902, the RF return current travels “around” the slot 902. This causes an area of RF current concentration at the lateral edges of the slot 902, and an area of low RF current to the top and bottom of the slot, thereby causing an azimuthal asymmetric perturbation in RF current flow, as illustrated in FIG. 1B.
FIG. 1B illustrates a schematic view of the traditional chamber liner 90 from line A-A to line B-B for indicating asymmetric RF current flow according to FIG. 1A. As shown in FIG. 1B, RF current flow (shown by dotted lines I90) is perturbed by the slot 902, that is, the slot 902 creates area of high concentration I92 which can lead to an azimuthal asymmetry in the electromagnetic fields and ultimately the plasma casing non-uniform etch rate relative to the slot 902.
The electrical skews could hardly be prevented in the plasma process because the traditional chamber liner failed to provide a balanced RF current flow and led to the defective plasma process. It is important that the RF current distribution within the chamber be symmetric, such that the electromagnetic fields for the plasma to provide the uniform azimuthal etch or deposition rate. Therefore, a need exists for balancing RF current flow along the chamber liner that prevents the above-mentioned problems.